Continuity mistake: When Navin is at the gas station and is being shot at by the sniper, take a look at the arrangement of the oil cans on the rack beside him. One of the cans in the middle of the rack changes color from pink to purple, and some labels turn, between shots.
Continuity mistake: When the paper airplane flies into the classroom in the wideshot, there's a guy wearing a striped shirt sitting at the back who vanishes in the next closeup. (00:16:10)